Electric circuit breaker



Oct. 13, 1931. 1 c. GRANT.

ELECTRIC CIRCUIT BREAKER Filed Gct. 26, 1928 Patented Oct. 13, 1931 UNITED STATES PATENT OFFICE LEWIS COLIN GRANT, 0F NEWCASTLE-UPON-TYNE, ENGLAND, ASSIGNOR TO ELEC- TRICAL IMPROVEMENTS LIMITED, OF NEWCASTLE-UPON-TYNE, ENGLAND, A COM- PANY OF GREAT BRITAIN ELECTRIC CIRCUIT BREAKER Application led October 26, 1928, Serial No. 315,305, and in Great Britain November 7, 1927.

This invention relates to electric circuitbreakers, its object being the construction of a circuitbreaker in which the arc formed on the opening of the circuit shall be very quickly quenched.

The invention relates more particularly to circuit-breakers having an arc-quenching delvice in the form of a series of conducting discs or baiiles which surround the movable Contactin close proximity to it as it commences its opening movement.

ln an electric circuit-breaker according to this invention the arc-quenching device comprises a series of conducting discs or like members insulated and slightly separated from each other, the edges of the discs being closely surrounded by a casing or wall which forms a boundary to the spaces between the discs, the moving contact of the circuitbreaker passing through an aperture in the discs. These discs are conveniently separated and supported by insulating rings or like members which surround the edges of the discs and may constitute the casing or Wall referred to as forming the boundary of the spaces between the discs.

The discs may be of appreciable thickness, say for example half-aninch, and are preerably formed with an annular groove on each face so that when the discs are assembled the narrow spaces between them merge into larger annular chambers formed by the grooves in the.neighboring faces.

The discs themselves may have radial passages leading from the central apertures to other passages or openings for the circulation of oil or gaseous products.

In the accompanying drawings,

Figure l is a diagrammatic sectional elevation of one construction of circuit-breaker according to this invention,

igure' is a plan view of one of the discs, an

Figure 3 is a perspective view showing diagrammatically a three-phase double-break circuit-breaker having the improved arcquenching devices.

With reference first to Figure l, the'circuit-breaker represented diagrammatically has a fixed contact A and a. movable contact A1 mounted in insulators in a tank or casing B. With the details of construction and the connections to the contacts the present invention is not concerned, but it is assumed that the circuit is opened by withdrawing the rod A2 and raising the movable contact A1 into the position shown in dotted lines.

Within the casing B is a series of discs C, say of copper or other conducting material, placed one above the other so that their cen tral apertures C1 form a passage whose wall closely surrounds the movable contact A1 as it moves upwards to open the circuit.

These discs C are supported and held by rings of insulating material D secured by bolts E, some of the rings D1 serving to separate adjacent discs so that narrow spaces F are left between them. These spaces may be quite narrow, i. e. the' separation of the discs very small. For instance, supposing the thickness of each disc to be say half-aninch, the separating spaces might be onesixteenth of an inch or less.

On each face of each disc an annular groove C2 is formed and when the discs are placed in position the grooves on adjacent faces register and form an annular chamber round the edge of the space F. These chambers are closed by the separating rings D1 in the construction illustrated although that is not necessarily always the case.

Each disc is provided with radial passages C3 leading from the central aperture C1 to a vertical hole or passage G passing through all the discs and separating rings and affording a path for the circulation of oil if the arrangement is oil-immersed.

Four discs are shown as occupying the lower portion of the tank or casing B. This number may vary and will depend upon the length of the opening movement of the movable Contact A1, the power with which the circuit-breaker has to deal and other factors. A space above the discs beneath the top plate of the tank B forms an expansion chamber. The dimensions of this space may vary and in some instances the discs C may practically fill the casing.

The diagrammatic perspective view forming Figure 3 shows one way in which the improved arc-quenching devices may be emodied in a three-phase double-break oilimmersed circuit-breaker. Each phase has two fixed contacts A3 mounted on conductors A4t in connection with the terminals A5. Each pair of conduct-ors A* is mechanically connected but electrically insulated by bridging pieces A and all three sets of iixed contacts are mounted on a bar A1 supported by rods A8 from the top plate BlL of the tank B2.

Fixed adjacent to each contact As is an arc-quenching device I-I. The construction of these is not indicated in detail in Figure 3 but it is to be understood that it is similar to the construction described with reference to Figure l, each arc-quenching device comprising a series of closely spaced and insulated conducting discs having a central aperture closely surrounding the movable contacts. The wall or casing forming the boundar to the spaces between the discs would in igure 3 be constituted by the supporting and separating rings of insulating material such as are referred to as D and D1 in Figure 1.

Each phase switch has two movable contacts represented in Figure 3 at A". These may be formed by the turned-down ends of a common conducting bar and, as indicated in that ligure, all three pairs of movable contacts, the pairs being suitably insulated from each other, are supported from a bar A1o having operating rods` A1L1 which pass out through suitable openings in the tank cover.

The present invention is not concerned with the details of construction of the parts of the circuit-breaker other than the arcquenching devices and hence those parts are merely represented diagrammatically.

The improved arc-quenching device is found to be very efficient in practice, a circuitbreaker of given size breaking satisfactorily circuits of much higher power than can be dealt with by circuit-breakers of the same size and of the usual type. Its eliciency is probably due to a variety of causes, such as the close spacing of the discs, the provision of. the enlarged annular chambers into which the spaces lead, and to the radial passages leadin into the circulatory holes or passages throng the discs and their supports.

An important factor is probably that the spaces between the discs are not o en on their outer edges to the oil or other uid in the circuit-breaker casing but are surrounded by the wall formed by the insulating rings .or

by some other enclosing member, as for 1nstance the casing of the circuit-breaker itself which in some constructions, such as that illustrated in Figure l, is in close proximity to the arc-quenching device.

What I claim as my invention and desire to secure by Letters Patent is s l. In an electric circuit-breaker the combination with a. moving contact, of an arcquenching device comprising a series of conducting discs insulated from one another and separated rom one another by a distance which is small relative to their thickness, the edges of the discs being closely surrounded by a casing forming a boundary to the spaces between the discs, and the discs being provided with aligned apertures through which the moving contact passes.

2. In an electric circuit-breaker the combination with a moving contact, of an arcquenchin device comprising a series of conducting iscs through which the moving contact passes and a series of insulating rings for sup orting said discs so that they are insulated rom one another and are separated from one another by a distance which is small relative to their thickness, said insulating rings grming a wall surrounding the edges of the scs.

3. In an electric circuit-breaker the combination with a moving contact of an arcuenching device comprising a series of conucting discs insulated and slightly separated from one another each disc being formed with an annular oove on each face such grooves in adjacent iscs cooperating to form a larger annular chamber in the narrow space between said adjacent discs, the edges of the discs being closely surrounded by a casing forming a boundary to the spaces between the discs and the discs being rovided with aligned apertures through which the moving contact passes.

4. In an electric circuit-breaker the combination with a moving contact of an arcquenching device comprising a series of conducting discs having aligned apertures through which the moving contact passes and a series of insulating rings for supporting said discs so that they are insulated and separated from each other and for forming a wall surrounding the edges of the discs, each disc being formed with an annular groove so that when the discs are assembled the narrow spaces between them merge into larger annular chambers.

5. In an electric circuit-breaker the combination with a moving contact of an arcquenching device comprising a series of conducting iscs having aligned central apertures through which the moving contact passes and radial passages leading from the central aperture to other passages or openings or t e circulation of oil or gaseous products, discs being insulated and slightly separated from each other and the edges of the discs being closely surrounded by a casing forming a boundary to the spaces between the discs.

6, In an electric circuit-breaker the combination with a moving contact of an arcquenchin device comprising a series o conducting iscs having aligned central apertures through which the moving contact passes and radial passages leading from the central aperture to other passages or openings for the circulation of oil or gaseous productsl and a series of insulating rings for supporting said discs so that they are insulated and separated from each other and for forming a Wall surrounding the edges of the discs.

7. In an electric circuit-breaker the combination With a moving Contact of an arcquenchin device comprising a series of conducting iscs having aligned central apertures through which the moving contact passes and radial passages leading from the central aperture to other passages or openings for the circulation of oil or gaseous products and a series of insulating rings for supporting said discs so that they are insulated and separated from each other and for forming a Wall surrounding the edges of the discs,

each disc being formed With an annular groove so that when the discs are assembled the narrow spaces between them merge into larger annular chambers.

8. An electric circuit-breaker comprising a tank, insulating oil in said tank, a fixed contact mounted therein and a moving contact supported thereby, a series of conducting discs having aligned apertures through which the moving contact passes and a series of insulating rings for supporting said .discs in the tank so that they are insulated from one another and separated from one another by aI space in Which the oil circulates, the tank being formed so that it surrounds closely said insulating rings. i

In testimony whereof I have signed my name to this specification.

LEWIS COLIN GRANT. 

